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Bis[tris(cyclohexyl)tin] azide hydroxide (Cy3Sn)2N3(OH) X-ray structure determination and comparison with analogous compounds.

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APPLIED ORGANOMETALLIC CHEMISTRY
Appl. Organometal. Chem. 2005; 19: 356–359
Main
Published online in Wiley InterScience (www.interscience.wiley.com). DOI:10.1002/aoc.822
Group Metal Compounds
Bis[tris(cyclohexyl)tin] azide hydroxide,
(Cy3Sn)2N3(OH): X-ray structure determination
and comparison with analogous compounds
R. Alan Howie1 *, James L. Wardell2 and Solange M. S. V. Wardell3
1
Department of Chemistry, University of Aberdeen, Old Aberdeen AB24 3UE, Scotland, UK
Departamento de Quı́mica Inorgânica, Instituto de Quı́mica, Universidade Federal do Rio de Janeiro, CP 68563, 21945-970 Rio de
Janeiro, RJ, Brazil
3
Far-Manguinhos, Fiocruz, Rua Sizenando Nabuco 100, Manguinhos, CEP 21041-250, Rio de Janeiro, RJ, Brazil
2
Received 23 August 2004; Revised 30 August 2004; Accepted 16 September 2004
The structure of bis[tris(cyclohexyl)tin] azide hydroxide, (Cy3 Sn)2 N3 (OH) (1), contains infinite chains
of molecules linked by regularly alternating and µ2 bridging azide and hydroxide groups that
create trigonal bipyramidal tin centres. The bridges, with Sn–N 2.436(11) and 2.385(11) Å and
Sn–O 2.199(8) and 2.197(8) Å, are relatively symmetrical. This structure is similar to that of catena
bis(trimethyltin) azide hydroxide, (Me3 Sn)2 N3 (OH) (2). In the structure of 1, each terminal nitrogen
atom of the azide is bonded to a different tin atom (1,3 or α,γ bridge formation). In the structure of
2, however, only one nitrogen atom of each azide is involved in bridging and bonds to two different
tin atoms (1,1 or α,α bridge formation). In this case, the remaining terminal nitrogen atoms act as
acceptors for O–H· · ·N hydrogen bonds that link the chains to form infinite sheets. It appears then,
from these two examples, that in such compounds the size of the organic species bonded to tin can
affect the azide bridging mode and also the packing of the polymeric chains Copyright  2005 John
Wiley & Sons, Ltd.
KEYWORDS: tris(cyclohexyl)tin; pseudo-halostannane; azide; crystal structure
INTRODUCTION
Tris(cyclohexyl)tin compounds have attracted much commercial interest, especially in the area of agrochemicals,
the best example being tris(cyclohexyl)tin hydroxide, PLICTRAN, a well used and effective acaricide.1 Owing in part
to such use, much study has been made of the syntheses
and structures of tris(cyclohexyl)tin compounds in general,
as can be readily seen in the Cambridge Structural Database.2
Our studies on tris(cyclohexyl)tin compounds stem from an
interest in the effect of the bulk of organic groups in triorganotin halides and pseudohalides on coordination at the
tin centre.3,4 In the course of our studies we encountered
bis[tris(cyclohexyl)tin] azide hydroxide, (Cy3 Sn)2 N3 (OH) (1),
as the wholly unexpected product of the attempted recrystallization of tris(cyclohexyl)tin azide, Cy3 SnN3 , from ethanol.
*Correspondence to: R. Alan Howie, Department of Chemistry,
University of Aberdeen, Old Aberdeen AB24 3UE, Scotland, UK.
E-mail: r.a.howie@abdn.ac.uk
Contract/grant sponsor: CNPq, Brazil.
The characterization of 1 rests entirely upon the X-ray
structure analysis reported here. The tendency for triorganotin azides to undergo partial hydrolysis has been noted
previously,5,6 as in the formation of trimethyltin azide hydroxide, (Me3 Sn)2 N3 (OH) (2), from the parent trimethyltin azide,
Me3 SnN3 (3). It is of some interest to compare the structure of
1 with those of 2 and 3 and other related compounds in terms
of Sn–O and Sn–N bond lengths and the presence or absence
of bridging.
RESULTS AND DISCUSSION
The asymmetric unit of 1 is shown in Fig. 1, and selected
bond lengths and angles are given in Table 1. It occurs,
Fig. 2, in the form of zig-zag polymeric chains propagated
in the direction of a in which µ2 bridging azide and
hydroxyl groups alternate along the length of the chain.
This creates trigonal bipyramidal tin centres with the
azide and hydroxyl groups axial and equatorial cyclohexyl
Copyright  2005 John Wiley & Sons, Ltd.
Main Group Metal Compounds
Structure of (Cy3 Sn)2 N3 (OH)
Table 1. Selected bond lengths (Å) and angles (◦ ) for 1
Sn1–C1
Sn1–C7
Sn1–C13
Sn1–N1
Sn1–O1
N1–N2
C1–Sn1–C7
C1–Sn1–C13
C7–Sn1–C13
N1–Sn1–C1
N1–Sn1–C7
N1–Sn1–C13
O1–Sn1–C1
O1–Sn1–C7
O1–Sn1–C13
N1–Sn1–O1
Sn1–N1–N2
Sn1–O1–Sn2ii
2.172(13)
2.124(11)
2.177(16)
2.436(11)
2.199(8)
1.160(14)
122.7(5)
119.3(7)
115.7(6)
86.1(4)
84.9(4)
83.9(6)
92.0(4)
97.9(4)
95.1(5)
177.1(4)
123.1(9)
140.0(5)
Sn2–C19
Sn2–C25
Sn2–C31
Sn2–N3
Sn2–O1i
N2–N3
C19–Sn2–C25
C19–Sn2–C31
C25–Sn2–C31
N3–Sn2–C19
N3–Sn2–C25
N3–Sn2–C31
O1i –Sn2–C19
O1i –Sn2–C25
O1i –Sn2–C31
N3–Sn2–O1i
Sn2–N3–N2
N1–N2–N3
2.170(12)
2.137(14)
2.158(13)
2.385(11)
2.197(8)
1.206(14)
125.2(5)
110.2(5)
123.2(5)
84.6(5)
85.3(4)
88.1(5)
95.6(4)
93.1(4)
93.6(5)
178.1(4)
127.5(9)
176.7(13)
Figure 1. The asymmetric unit of 1. Non-hydrogen atoms
are shown as 20% probability displacement ellipsoids and all
hydrogen atoms and the carbon atoms of the B component of
the disordered cyclohexyl groups have been omitted for clarity.
Symmetry codes: (i) x − 1/2, 3/2 − y, z; (ii) x + 1/2, 3/2 − y, z.
groups. The hydroxyl groups with Sn–O distances of
2.197(8) and 2.199(8) Å and Sn–O–Sn angle of 140.0(5)◦
bridge in a symmetrical manner, and the azide groups with
Sn–N distances of 2.385(11) and 2.436(11) Å and Sn–N–N
angles of 123.1(9) and 127.5(9)◦ bridge only slightly less
symmetrically. All of the cyclohexyl rings are in the chair
conformation, with C–C distances and internal C–C–C
angles more or less as expected, provided that due allowance
is made for the disorder noted in the Experimental section
below.
The only close analogues to 1 for which structural data are
available in the Cambridge Structural Database2 are 27 and the
corresponding isocyanate hydroxide, (Me3 Sn)2 (NCO)(OH)
(4).8 It is possible, however, to compare the situations of
the azide and hydroxide ligands in the structure of 1 with
those found in a wider range of compounds. As shown
in Table 2, in compounds of the form R3 SnN3 with bulky
R [R = 2-methyl-2-phenylpropyl (Neo) and t Bu],3,9 azide
Figure 2. Part of a chain of molecules of 1 propagated in the
direction of a (left to right across the page). For clarity, cyclohexyl
groups are represented by the carbon atoms directly bonded
to tin and labelled Cy(n). All non-hydrogen atoms shown are
represented as 50% probability displacement ellipsoids and
hydrogen atoms as spheres of arbitrary radii. Symmetry codes:
(i) x − 1/2, 3/2 − y, z; (ii) x + 1/2, 3/2 − y, z.
functions as a monodentate ligand. With less-bulky R, azide
fulfils a µ2 bridging function either in α,α mode (R = Me),10
where only one terminal nitrogen atom forms the bridging
bonds, or in α,γ mode (R = phenyl,11 benzyl12 ), where
both terminal nitrogen atoms are involved. Also notable
in Table 2 is the α,α bridging mode of azide in the azide
Table 2. Comparison of Sn–N and N–N bond lengths (Å) in 4- and 5-coordinate triorganotin azides
4-coordinate Sn
t
5-coordinate Sn
Bond
Bu3 SnN3
at 293 K
Ref. 9
(Neo)3 SnN3
at 150 K
Ref. 3
Me3 SnN3
at RT Ref. 10
α,αN3
(Me3 Sn)2 N3 (OH)
at RT Ref. 7
α,αN3
Ph3 SnN3
at RT Ref. 11
α,γ N3
(PhCH2 )3 SnN3
at 293 K Ref. 12
α,γ N3
(Cy3 Sn)2 N3 (OH)
at 120 K This
work α,γ N3
Sn–Nα
Sn–N
Nα –Nβ
Nβ –Nχ
2.101(4)
—a
1.188(7)
1.121(8)
2.247(4)
—a
—b
—b
2.386(3)
2.386(3)
1.218(9)
1.145(10)
2.439(17)
2.613(17)
1.16(3)
1.20(3)
2.186(3)
2.714(4)
1.194(4)
1.146(4)
2.157(10)
2.546(11)
1.078(13)
1.087(14)
2.385(11)
2.436(11)
1.206(14)
1.160(14)
a Monodentate N .
3
b Limited refinement
renders N–N distances imprecise.
Copyright  2005 John Wiley & Sons, Ltd.
Appl. Organometal. Chem. 2005; 19: 356–359
357
358
Main Group Metal Compounds
R. Alan Howie, James L. Wardell and Solange M. S. V. Wardell
hydroxide 2, with R = Me, as distinct from the α,γ mode
of bridging in 1, with R = cyclohexyl. This implies that
the difference in azide bridging mode between 1 and 2 is
brought about, as for the simple azides, by the difference
in the bulk of the organic R species, Cy as against Me. It
is clear that the bulk of the organic R groups will control
the closeness of approach of adjacent tin centres and, thus,
determine whether bridging can occur and, if it does, in what
mode.
Table 3 shows Sn–O bond lengths in a variety of
triorganotin hydroxyl compounds. The trimesityl compound
is the only molecular structure and has the shortest Sn–O
bond. All of the other compounds shown are linear polymers.
In isostructural 2 and 4, the polymer chains are propagated by
regular alternation of pseudohalide (azide in 2 and isocyanate
in 4) and hydroxyl groups. In both cases the pseudohalide
groups bridge in α,α mode and the remaining terminal
nitrogen atoms of the azides in 2 and the oxygen atoms of
the isothiocyanates in 4 act as acceptors for hydrogen bonds,
with the hydroxyl groups of adjacent polymer chains as
donors. In this way, polymeric sheets are produced (Fig. 3).
In contrast, in 1 there is no hydrogen bonding between
the polymer chains. Indeed, there are only van der Waals
interactions between neighbouring chains. The small bulk
of the organic groups, methyl in both 2 and 4, is also
implicated here, because, in these cases, it allows the chains
to pack together closely enough for hydrogen bonding to take
place.
CONCLUSIONS
The structure of bis[tris(cyclohexyl)tin] azide hydroxide
(1), as determined by X-ray crystallography, is shown to
be that of a linear polymer with regularly alternating µ2
azide and hydroxyl groups. Comparison with a number of
other triorganotin azides and hydroxides suggests that the
azide bridging mode is dependent upon the the bulkiness
of the organic groups attached to tin. The difference
between the purely linear polymeric structure of 1 and
the two-dimensional polymeric structure of its trimethyl
analogue, brought about in the latter by the formation
of O–H· · ·N hydrogen bonds between adjacent chains, is
likewise attributed to the difference in size of the organic
groups attached to tin.
Figure 3. A layer of molecules of (Me3 Sn)2 N3 (OH) (2). The
layer is parallel to (100) and centred on x = 1/4. Dashed lines
indicate the O–H· · ·N hydrogen bonds. Symmetry codes: (i) x,
y, z − 1; (ii) x, y, z + 1; (iii) 1/2 − x, 1/2 + y, 1/2 − z; (iv) 1/2 − x,
1/2 + y, −z − 1/2; (v) 1/2 − x, 1/2 + y, 3/2 − z; (vi) x, y + 1,
z; (vii) x, y + 1, z − 1; (viii) x, y + 1, z + 1.
EXPERIMENTAL
Preparation of tris(cyclohexyl)tin azide,
Cy3 SnN3 , and growth of crystals of 1
A solution of (Cy)3 SnCl (2 mmol) in Me2 CO (15 ml) and a
suspension of NaN3 (5 mmol) in Me2 CO (15 ml) were mixed.
After stirring at room temperature overnight, the reaction
mixture was filtered. The filtrate was shaken with a further
suspension of NaN3 (5 mmol) in Me2 CO (15 ml) for 4 h, all
volatiles removed by rotary evaporation and the residue
extracted into CHCl3 . The chloroform extract was dried and
rotary evaporated to leave a solid residue.
Crystallization of this residue from EtOH gave
bis[tris(cyclohexyl)tin] azide hydroxide, (Cy3 Sn)2 N3 (OH) (1),
as determined by X-ray crystallography. M.p. 133–136 ◦ C.
X-ray crystallography
Intensity data were collected at 120(2) K, by means of the
Enraf Nonius KappaCCD area detector diffractometer of
the EPSRC’s crystallography service at Southampton, for
a colourless crystal, 0.20 × 0.30 × 0.35 mm3 , with Mo Kα
radiation, λ = 0.710 73 Å so that θmax = 27.5◦ . The entire
process of data collection, cell refinement and data reduction
was accomplished by means of the programs DENZO16
Table 3. Comparison of Sn–O bond lengths (Å) in 4- and 5-coordinate triorganotin hydroxyl compounds
5-coordinate Sn
Bond
4-coordinate Sn
(Mesityl)3 SnOH
at RT Ref. 13
[Ph3 SnOH]n at RT
Ref. 14
[Et3 SnOH]n
at RT Ref. 15
(Cy3 Sn)2 N3 (OH)
at 150 K This work
(Me3 Sn)2 N3 (OH)
at RT Ref. 7
(Me3 Sn)2 (NCO)(OH)
at RT Ref. 8
Sn–O
Sn–O
1.999(6)
—
2.197(5)
2.255(5)
2.155(5)
2.244(5)
2.197(8)
2.199(8)
2.093(13)
2.211(13)
2.14(5)
2.15(5)
Copyright  2005 John Wiley & Sons, Ltd.
Appl. Organometal. Chem. 2005; 19: 356–359
Main Group Metal Compounds
and COLLECT.17 Correction for absorption by a semiempirical method based upon the variation in intensity
of equivalent reflections was achieved with the program
SORTAV.18,19 The initial structure solution was obtained by
the heavy-atom technique with the program SHELXS-8620
and completed and refined by full-matrix least squares on
F2 with SHELXL-97.21 In order to accommodate disorder in
two of the cyclohexyl groups, one associated with each of
the two tin atoms, atoms C(15), C(18) and C(32–36) were
split into pairs as, for example, C(15A)/C(15B), with the
atoms of each pair now in sites with occupancy factors
of 0.5 and refined with isotropic displacement parameters
and with restraints applied to the C–C distances and
internal C–C–C angles of the disordered rings. Anisotropic
thermal vibration parameters were refined for all other
non-hydrogen atoms. In the final stages of refinement,
hydrogen atoms were introduced in calculated positions,
taking full account of the disorder noted above, and
refined with a riding model. The program ORTEP-3 for
Windows22 was used in the preparation of the figures, and
SHELXL-97 and PLATON23 were used for bond lengths
and angles and other molecular geometry calculations.
PLATON was used, in particular, for calculations based
upon crystallographic data extracted from the Cambridge
Structural Database.2
Crystal data
Formula: C36 H67 N3 OSn2 ; M = 795.31; orthorhombic, Pna21 ,
a = 19.9546(15) Å, b = 17.2336(11) Å, c = 10.9161(6) Å, Z =
3
4, V = 3753.9(4) Å , 6249 independent reflections (Rint =
0.050), 5481 observed reflections [I > 2σ (I)]; parameters
refined: 373; number of restraints: 134; Flack parameter:24
−0.03(7); R(F): 0.075 (obs. data); wR(F2 ) = 0.178 (all data);
−3
ρmax = 3.42 e− Å (<0.90 Å from tin). CCDC deposition no:
231210.
Acknowledgements
We are indebted to the EPSRC for the use of both the Chemical
Database Service at Daresbury, primarily for access to the Cambridge
Structural Database, and the X-ray service at the University of
Southampton for data collection. We thank CNPq, Brazil, for financial
support.
Copyright  2005 John Wiley & Sons, Ltd.
Structure of (Cy3 Sn)2 N3 (OH)
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